U.S. patent number 11,351,842 [Application Number 16/743,583] was granted by the patent office on 2022-06-07 for cascade heat transfer system.
This patent grant is currently assigned to Thermo King Corporation. The grantee listed for this patent is THERMO KING CORPORATION. Invention is credited to Jeffrey B. Berge, Michal Kolda, Stephen A. Kujak, John R. Sauls, Kenneth J. Schultz, Panayu Robert Srichai, Vladimir Sulc.
United States Patent |
11,351,842 |
Kujak , et al. |
June 7, 2022 |
Cascade heat transfer system
Abstract
A transport refrigeration system (TRS) includes a first heat
transfer circuit including a first compressor, a condenser, a first
expansion device, and a cascade heat exchanger. The first
compressor, the condenser, the first expansion device, and the
cascade heat exchanger are in fluid communication such that a first
heat transfer fluid can flow therethrough. The TRS includes a
second heat transfer circuit including a second compressor, the
cascade heat exchanger, a second expansion device, and an
evaporator. The second compressor, the cascade heat exchanger, the
second expansion device, and the evaporator are in fluid
communication such that a second heat transfer fluid can flow
therethrough. The first heat transfer circuit and the second heat
transfer circuit are arranged in thermal communication at the
cascade heat exchanger such that the first heat transfer fluid and
the second heat transfer fluid are in a heat exchange relationship
at the cascade heat exchanger.
Inventors: |
Kujak; Stephen A. (Brownsville,
MN), Schultz; Kenneth J. (Onalaska, MN), Berge; Jeffrey
B. (Eden Prairie, MN), Srichai; Panayu Robert
(Minneapolis, MN), Sulc; Vladimir (Minnetonka, MN),
Kolda; Michal (Prague, CZ), Sauls; John R. (La
Crosse, MN) |
Applicant: |
Name |
City |
State |
Country |
Type |
THERMO KING CORPORATION |
Minneapolis |
MN |
US |
|
|
Assignee: |
Thermo King Corporation
(Minneapolis, MN)
|
Family
ID: |
57749758 |
Appl.
No.: |
16/743,583 |
Filed: |
January 15, 2020 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20200148038 A1 |
May 14, 2020 |
|
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
15392581 |
Dec 28, 2016 |
10543737 |
|
|
|
62271872 |
Dec 28, 2015 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60H
1/323 (20130101); F25B 7/00 (20130101); F25B
43/006 (20130101); F25B 9/008 (20130101); F25B
13/00 (20130101); B60H 1/3228 (20190501); F25B
40/00 (20130101); B60H 1/3226 (20130101); B60H
2001/3289 (20130101); F25B 2400/13 (20130101) |
Current International
Class: |
F25B
7/00 (20060101); B60H 1/32 (20060101); F25B
13/00 (20060101); F25B 43/00 (20060101); F25B
40/00 (20060101); F25B 9/00 (20060101) |
Field of
Search: |
;62/79 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
102014200160 |
|
Jul 2015 |
|
DE |
|
2131122 |
|
Dec 2009 |
|
EP |
|
2924372 |
|
Sep 2015 |
|
EP |
|
2014/030238 |
|
Feb 2014 |
|
WO |
|
2014082069 |
|
May 2014 |
|
WO |
|
WO-2014082069 |
|
May 2014 |
|
WO |
|
2014199445 |
|
Feb 2017 |
|
WO |
|
Other References
European Search Report, issued in corresponding European
Application No. 16207174.0 dated Sep. 29, 2020, 5 pages. cited by
applicant .
Bansal; "Thermodynamic analysis of an R744-R717 cascade
refrigeration system"; Department of Mechanical Engineering,
International Journal of Refrigeration, 2008, vol. 31, pp. 45-54.
cited by applicant .
European Search Report issued in corresponding European Application
No. 16207174.0 dated Apr. 28, 2017 (9 pages). cited by applicant
.
Kim G. Christensen: "The World's first McDonald's restaurant using
natural refrigerants"; Danish Technological Institute,
Refrigeration science and technology, 2004, pp. 1-9. cited by
applicant .
Techline: "An exchange of technical information about carrier
transicold container products"; NaturaLINE Unit, Jun. 2013, vol.
19, No. 1, pp. 1-6. cited by applicant.
|
Primary Examiner: Crenshaw; Henry T
Assistant Examiner: Tavakoldavani; Kamran
Attorney, Agent or Firm: Hamre, Schumann, Mueller &
Larson, P.C.
Claims
What is claimed is:
1. A transport refrigeration system (TRS), comprising: a first heat
transfer circuit, including: a first compressor, a condenser, a
first expansion device, and a cascade heat exchanger, wherein the
first compressor, the condenser, the first expansion device, and
the cascade heat exchanger are in fluid communication such that a
first heat transfer fluid can flow therethrough; and a second heat
transfer circuit, including: the cascade heat exchanger, and an
evaporator, wherein the cascade heat exchanger and the evaporator
are in fluid communication such that a second heat transfer fluid
can flow therethrough; wherein the first heat transfer circuit and
the second heat transfer circuit are arranged in thermal
communication at the cascade heat exchanger such that the first
heat transfer fluid and the second heat transfer fluid are in a
heat exchange relationship at the cascade heat exchanger, wherein
the transport refrigeration system is configured to control one or
more environmental conditions within a conditioned space of a
transport unit, wherein the first heat transfer circuit is
configured such that the first heat transfer fluid is directed from
the first compressor directly to the condenser, and wherein the
first heat transfer fluid and the second heat transfer fluid are
different heat transfer fluids.
2. The TRS according to claim 1, further comprising an engine
configured to provide mechanical power to the first compressor.
3. The TRS according to claim 1, wherein the first heat transfer
fluid has a relatively low global warming potential (GWP).
4. The TRS according to claim 3, wherein the first heat transfer
fluid is one of an unsaturated hydrofluorocarbon (HFC), a
hydrofluoroolefin (HFO), a hydrocarbon (HC), ammonia, or carbon
dioxide (CO.sub.2).
5. The TRS according to claim 1, wherein the second heat transfer
fluid is carbon dioxide (CO.sub.2).
6. The TRS according to claim 1, wherein the first heat transfer
circuit includes one or more of a suction-liquid heat exchanger and
an economizer.
7. The TRS according to claim 1, wherein the evaporator of the
second heat transfer circuit is in thermal communication with the
conditioned space.
8. The transport refrigeration system of claim 1, wherein the
second heat transfer circuit further includes one or more of a
hot-gas bypass, an intercooler, a suction-liquid heat exchanger,
and an economizer.
9. The transport refrigeration system of claim 5, wherein the first
heat transfer circuit and the second heat transfer circuit are
separate circuits such that the first heat transfer fluid is
fluidly isolated from the second heat transfer fluid.
10. A system, comprising: a first heat transfer circuit, including:
a first compressor, a condenser, a first expansion device, and a
cascade heat exchanger, wherein the first compressor, the
condenser, the first expansion device, and the cascade heat
exchanger are in fluid communication such that a first heat
transfer fluid can flow therethrough; and a second heat transfer
circuit, including: the cascade heat exchanger and an evaporator,
wherein the cascade heat exchanger and the evaporator are in fluid
communication such that a second heat transfer fluid can flow
therethrough; wherein the first heat transfer circuit and the
second heat transfer circuit are arranged in thermal communication
at the cascade heat exchanger such that the first heat transfer
fluid and the second heat transfer fluid are in a heat exchange
relationship at the cascade heat exchanger, wherein the first heat
transfer circuit is configured such that the first heat transfer
fluid is directed from the first compressor directly to the
condenser, and wherein the first heat transfer fluid and the second
heat transfer fluid are different heat transfer fluids.
11. The system according to claim 10, wherein the first heat
transfer fluid has a relatively low global warming potential
(GWP).
12. The system according to claim 11, wherein the first heat
transfer fluid is one of an unsaturated hydrofluorocarbon (HFC), a
hydrofluoroolefin (HFO), a hydrocarbon (HC), ammonia, or carbon
dioxide (CO.sub.2).
13. The system according to claim 10, wherein the second heat
transfer fluid is carbon dioxide (CO.sub.2).
14. The system according to claim 10, wherein the first heat
transfer circuit further includes one or more of a suction-liquid
heat exchanger and an economizer.
15. The system according to claim 10, wherein the evaporator of the
second heat transfer circuit is in thermal communication with a
conditioned space.
16. The system of claim 10, wherein the second heat transfer
circuit further includes one or more of a hot-gas bypass, an
intercooler, a suction-liquid heat exchanger, and an
economizer.
17. The system of claim 10, wherein the first heat transfer circuit
and the second heat transfer circuit are separate circuits such
that the first heat transfer fluid is fluidly isolated from the
second heat transfer fluid.
18. A method of heat transfer in a transport refrigeration system
(TRS), the TRS having a first heat transfer circuit and a second
heat transfer circuit in thermal communication via a cascade heat
exchanger, the method comprising: circulating a first heat transfer
fluid through the first heat transfer circuit, wherein circulating
the first heat transfer fluid through the first heat transfer
circuit includes directing the first heat transfer fluid from a
first compressor directly to a condenser; circulating a second heat
transfer fluid through the second heat transfer circuit; and
exchanging heat between the first heat transfer fluid and the
second heat transfer fluid via the cascade heat exchanger, wherein
the first heat transfer fluid and the second heat transfer fluid
are different heat transfer fluids.
19. The method according to claim 18, wherein exchanging heat
between the first heat transfer fluid and the second heat transfer
fluid via the cascade heat exchanger includes rejecting heat from
the second heat transfer fluid to the first heat transfer
fluid.
20. The method according to claim 18, wherein the second heat
transfer circuit is in thermal communication with a conditioned
space of a transport unit provided climate control by the TRS, and
the method further includes controlling one or more environmental
conditions in the conditioned space with the second heat transfer
circuit.
21. The method of claim 18, further comprising exchanging heat
between an evaporator in the second heat transfer circuit and the
conditioned space.
Description
FIELD
This disclosure relates generally to a transport refrigeration
system (TRS), More specifically, the disclosure relates to systems
and methods for providing a cascade heat exchange between a
plurality of heat transfer circuits in a TRS.
BACKGROUND
A transport refrigeration system (TRS) is generally used to control
one or more environmental conditions such as, but not limited to,
temperature, humidity, and/or air quality of a transport unit.
Examples of transport units include, but are not limited to, a
container (e.g., a container on a flat car, an intermodal
container, etc.), a truck, a boxcar, or other similar transport
units. A refrigerated transport unit is commonly used to transport
perishable items such as produce, frozen foods, and meat products.
Generally, the refrigerated transport unit includes a transport
unit and a TRS. The TRS includes a transport refrigeration unit
(TRU) that is attached to the transport unit to control one or more
environmental conditions (e.g., temperature, humidity, etc.) of a
particular space (e.g., a cargo space, a passenger space, etc.)
(generally referred to as a "conditioned space"). The TRU can
include, without limitation, a compressor, a condenser, an
expansion device, an evaporator, and one or more fans or blowers to
control the heat exchange between the air inside the conditioned
space and the ambient air outside of the refrigerated transport
unit.
SUMMARY
This disclosure relates generally to a transport refrigeration
system (TRS). More specifically, the disclosure relates to systems
and methods for providing a cascade heat exchange between a
plurality of heat transfer circuits in a TRS.
In an embodiment, the TRS includes a first heat transfer circuit
and a second heat transfer circuit in thermal communication. In an
embodiment the first heat transfer circuit includes a relatively
low global warming potential (GWP) heat transfer fluid and the
second heat transfer circuit includes a heat transfer fluid that is
carbon dioxide (CO.sub.2, also referred to as R-744).
In an embodiment, a heat transfer fluid having a relatively low GWP
includes, but is not limited to, unsaturated hydrofluorocarbons
(HFCs) such as hydrofluoroolefins (HFOs), hydrocarbons (HCs),
ammonia, and carbon dioxide (R-744).
A transport refrigeration system (TRS) is described. The TRS
includes a first heat transfer circuit including a first
compressor, a condenser, a first expansion device, and a cascade
heat exchanger. The first compressor, the condenser, the first
expansion device, and the cascade heat exchanger are in fluid
communication such that a first heat transfer fluid can flow
therethrough. The TRS includes a second heat transfer circuit
including a second compressor, the cascade heat exchanger, a second
expansion device, and an evaporator. The second compressor, the
cascade heat exchanger, the second expansion device, and the
evaporator are in fluid communication such that a second heat
transfer fluid can flow therethrough. The first heat transfer
circuit and the second heat transfer circuit are arranged in
thermal communication at the cascade heat exchanger such that the
first heat transfer fluid and the second heat transfer fluid are in
a heat exchange relationship at the cascade heat exchanger.
A system is also disclosed. The system includes an internal
combustion engine; a first heat transfer circuit, and a second heat
transfer circuit. The first heat transfer circuit includes a first
compressor, a condenser, a first expansion device, and a cascade
heat exchanger, wherein the first compressor, the condenser, the
first expansion device, and the cascade heat exchanger are in fluid
communication such that a first heat transfer fluid can flow
therethrough. The second heat transfer circuit includes a second
compressor, the cascade heat exchanger, a second expansion device,
and an evaporator, wherein the second compressor, the cascade heat
exchanger, the second expansion device, and the evaporator are in
fluid communication such that a second heat transfer fluid can flow
therethrough. The first heat transfer circuit and the second heat
transfer circuit are arranged in thermal communication at the
cascade heat exchanger such that the first heat transfer fluid and
the second heat transfer fluid are in a heat exchange relationship
at the cascade heat exchanger.
A method of heat transfer in a transport refrigeration system (TRS)
is also disclosed. The method includes providing a first heat
transfer circuit including a first compressor, a condenser, a first
expansion device, and a cascade heat exchanger, wherein the first
compressor, the condenser, the first expansion device, and the
cascade heat exchanger are in fluid communication such that a first
heat transfer fluid can flow therethrough, and a second heat
transfer circuit, including a second compressor, the cascade heat
exchanger, a second expansion device, and an evaporator, wherein
the second compressor, the cascade heat exchanger, the second
expansion device, and the evaporator are in fluid communication
such that a second heat transfer fluid can flow therethrough. The
method further includes disposing the first heat transfer circuit
and the second heat transfer circuit in thermal communication at
the cascade heat exchanger such that the first heat transfer fluid
and the second heat transfer fluid are in a heat exchange
relationship at the cascade heat exchanger.
BRIEF DESCRIPTION OF THE DRAWINGS
References are made to the accompanying drawings that form a part
of this disclosure, and which illustrate embodiments in which the
systems and methods described in this specification can be
practiced.
FIG. 1 illustrates a side view of a refrigerated transport unit,
according to an embodiment.
FIG. 2 is a schematic diagram of a heat transfer system for a
transport refrigeration system, according to an embodiment.
FIG. 3A is a schematic diagram of a reverse cycle heating/defrost
circuit for the heat transfer system of FIG. 2 for a transport
refrigeration system, according to an embodiment.
FIG. 3B is a schematic diagram of a hot gas bypass heating/defrost
circuit for the heat transfer system of FIG. 2 for a transport
refrigeration system, according to an embodiment.
FIG. 4A is a schematic diagram of a heat transfer system for a
transport refrigeration system, according to an embodiment.
FIG. 4B is a schematic diagram of a heat transfer system for a
transport refrigeration system, according to an embodiment.
Like reference numbers represent like parts throughout.
DETAILED DESCRIPTION
This disclosure relates generally to a transport refrigeration
system (TRS). More specifically, the disclosure relates to systems
and methods for providing a cascade heat exchange between a
plurality of heat transfer circuits in a TRS.
A TRS is generally used to control one or more environmental
conditions such as, but not limited to, temperature, humidity,
and/or air quality of a transport unit. Examples of transport units
include, but are not limited to, a container (e.g., a container on
a flat car, an intermodal container, etc.), a truck, a boxcar, or
other similar transport units. A refrigerated transport unit (e.g.,
a transport unit including a TRS) can be used to transport
perishable items such as, but not limited to, produce, frozen
foods, and meat products.
As disclosed in this specification, a TRS can include a transport
refrigeration unit (TRU) which is attached to a transport unit to
control one or more environmental conditions (e.g., temperature,
humidity, air quality, etc.) of an interior space of the
refrigerated transport unit. The TRU can include, without
limitation, a compressor, a condenser, an expansion valve, an
evaporator, and one or more fans or blowers to control the heat
exchange between the air within the interior space and the ambient
air outside of the refrigerated transport unit.
A "transport unit" includes, for example, a container (e.g., a
container on a flat car, an intermodal container, etc.), truck, a
boxcar, or other similar transport unit.
A "transport refrigeration system" (TRS) includes, for example, a
refrigeration system for controlling the refrigeration of an
interior space of a refrigerated transport unit. The TRS may
include a vapor-compressor type refrigeration system, a thermal
accumulator type system, or any other suitable refrigeration system
that can use refrigerant, cold plate technology, or the like.
A "refrigerated transport unit" includes, for example, a transport
unit having a TRS.
Embodiments of this disclosure may be used in any suitable
environmentally controlled transport apparatus, such as, but not
limited to, a shipboard container, an air cargo cabin, and an over
the road truck cabin.
Generally, a TRS may use hydrofluorocarbon (HFC) heat transfer
fluids (commonly referred to as a "refrigerant"). For example, one
commonly used HFC heat transfer fluid is R-404A (as identified
according to its American Society of Heating, Refrigerating, and
Air Conditioning Engineers ("ASHRAE") designation). The R-404A heat
transfer fluid, however, has a relatively high global warming
potential (GWP). The GWP of R-404A is 3,922 (on the 100 year GWP
time horizon, according to the Intergovernmental Panel on Climate
Change (IPCC Report 4)).
An increasing focus is being placed on replacing the HFC heat
transfer fluids with relatively lower GWP alternatives. Examples of
suitable alternatives include, but are not limited to, unsaturated
HFCs such as hydrofluoroolefins (HFOs), hydrocarbons (HCs),
ammonia, and carbon dioxide (CO.sub.2, also known by its ASHRAE
designation of R-744). Carbon dioxide, for example, has a GWP of 1.
These alternatives have a variety of advantages and disadvantages
such as, for example, safety risks (e.g., flammability, operating
pressure, etc.), thermophysical properties (e.g., relating to
efficiency of the TRS), cost, availability, or the like. In
general, embodiments described herein can reduce global warming
impact due to emissions of the heat transfer fluid into the
environment, optimize efficiency of the TRS and reduce an amount of
energy input to maintain a desired condition in a conditioned
space, or the like.
FIG. 1 illustrates a side view of a TRS 100 for a transport unit
125, according to an embodiment. The illustrated transport unit 125
is a trailer-type transport unit. Embodiments as described in this
specification can be used with other types of transport units. For
example, the transport unit 125 can represent a container (e.g., a
container on a flat car, an intermodal container, etc.), a truck, a
boxcar, or other similar type of refrigerated transport unit
including an environmentally controlled interior space.
The TRS 100 is configured to control one or more environmental
conditions such as, but not limited to, temperature, humidity,
and/or air quality of an interior space 150 of the transport unit
125. In an embodiment, the interior space 150 can alternatively be
referred to as the conditioned space 150, the cargo space 150, the
environmentally controlled space 150, or the like. In particular,
the TRS 100 is configured to transfer heat between the air inside
the interior space 150 and the ambient air outside of the transport
unit 125.
The interior space 150 can include one or more partitions or
internal walls (not shown) for at least partially dividing the
interior space 150 into a plurality of zones or compartments,
according to an embodiment. It is to be appreciated that the
interior space 150 may be divided into any number of zones and in
any configuration that is suitable for refrigeration of the
different zones. In some examples, each of the zones can have a set
point temperature that is the same or different from one
another.
The TRS 100 includes a transport refrigeration unit (TRU) 110. The
TRU 110 is provided on a front wall 130 of the transport unit 125.
The TRU 110 can include a prime mover (e.g., an internal combustion
engine) (not shown) that provides power to a component (e.g., a
compressor, etc.) of the TRS 100.
The TRU 110 includes a programmable TRS Controller 135 that
includes a single integrated control unit 140. It is to be
appreciated that, in an embodiment, The TRS controller 135 may
include a distributed network of TRS control elements (not shown).
The number of distributed control elements in a given network can
depend upon the particular application of the principles described
in this specification. The TRS Controller 135 can include a
processor, a memory, a clock, and an input/output (I/O) interface
(not shown). The TRS Controller 135 can include fewer or additional
components.
The TRU 110 also includes a heat transfer circuit (as shown and
described in FIG. 2). Generally, the TRS Controller 135 is
configured to control a heat transfer cycle (e.g., controlling the
heat transfer circuit of the TRU 110) of the TRS 100. In one
example, the TRS Controller 135 controls the heat transfer cycle of
the TRS 100 to obtain various operating conditions (e.g.,
temperature, humidity, air quality etc.) of the interior space
150.
FIG. 2 is a schematic diagram of a heat transfer system 200 for a
TRS (e.g., the TRS 100 of FIG. 1), according to an embodiment. The
heat transfer system 200 includes a first heat transfer circuit 205
and a second heat transfer circuit 210. In an embodiment, the first
heat transfer circuit 205 can alternatively be referred to as the
primary heat transfer circuit 205, the high side heat transfer
circuit 205, the condensing side heat transfer circuit 205, the
stage two heat transfer circuit, or the like. In an embodiment, the
second heat transfer circuit 210 can alternatively be referred to
as the low side heat transfer circuit 210, the evaporating side
heat transfer circuit 210, or the like. The first heat transfer
circuit 205 is in thermal communication with the second heat
transfer circuit 210.
The first heat transfer circuit 205 includes a compressor 220, a
condenser 230, a condenser fan 235, a first accumulator 240, a heat
exchanger 245, an expansion device 250, a cascade heat exchanger
255, and a second accumulator 260. The compressor 220, condenser
230, first accumulator 240, heat exchanger 245, expansion device
250, cascade heat exchanger 255, and second accumulator 260 are
fluidly connected to form the first heat transfer circuit 205 in
which a heat transfer fluid can circulate therethrough. The heat
transfer fluid can generally be a heat transfer fluid having a
relatively low global warming potential (GWP). Examples of suitable
heat transfer fluids for the first heat transfer circuit 205 can
include, but are not limited to, hydrofluoroolefins (HFOs),
hydrocarbons (HCs), and carbon dioxide (CO.sub.2) (also known by
its ASHRAE Standard 34 designation R-744), or the like.
In the illustrated embodiment, the compressor 220 is driven by a
power source 215. The power source 215 can be, for example, a part
of the TRU 110 (FIG. 1). The power source 215 (e.g., an internal
combustion engine, an electric drive motor, etc.) can provide
mechanical power directly to the compressor 220. The power source
215 can also provide mechanical power directly to a generator
(e.g., an alternator, etc.), which can be used to provide power
either to the compressor 220 or a second compressor 275 of the
second heat transfer circuit 210. In such an embodiment, the power
source 215 may include a converter between the generator and the
second compressor 275 to provide an appropriate power source for
the second compressor 275. In an embodiment in which the power
source 215 includes an electric drive motor that provides
mechanical power directly to the compressor 220 and/or the second
compressor 275, the electric power can come from any of a variety
of sources (e.g., batteries, shore power, etc.).
The second heat transfer circuit 210 includes the second compressor
275, the cascade heat exchanger 255, a third accumulator 280, a
second expansion device 285, an evaporator 290, and an evaporator
fan 295. The second compressor 275, cascade heat exchanger 255,
third accumulator 280, second expansion device 285, and evaporator
290 are fluidly connected to form the second heat transfer circuit
210 in which a heat transfer fluid can circulate therethrough. The
heat transfer fluid in the second heat transfer circuit 210 can
generally be different from the heat transfer fluid in the first
heat transfer circuit 205. The heat transfer fluid in the second
heat transfer circuit 210 can be, for example, R-744 (CO.sub.2).
The heat transfer fluid in the second heat transfer circuit 210 can
be selected, for example, based on its performance at relatively
low temperatures.
In operation, the heat transfer system 200 can be used to maintain
a desired condition in the interior space 150 of the transport unit
125. More particularly, the first heat transfer circuit 205 may
receive heat that is rejected from the second heat transfer circuit
210 via the cascade heat exchanger 255. The second heat transfer
circuit 210 can in turn be used to maintain the desired condition
within the interior space 150.
The first heat transfer circuit 205 can function according to
generally known principles in order to remove heat from the second
heat transfer circuit 210. The compressor 220 compresses the heat
transfer fluid from a relatively lower pressure gas to a relatively
higher-pressure gas. The relatively higher-pressure gas is
discharged from the compressor 220 and flows through the condenser
230. In accordance with generally known principles, the heat
transfer fluid flows through the condenser 230 and rejects heat to
a heat transfer fluid or medium (e.g., air, etc.), thereby cooling
the heat transfer fluid or medium. The condenser fan 235, in
accordance with generally known principles, can aid in removing the
heat from the heat transfer fluid in the first heat transfer
circuit 205. The cooled heat transfer medium which is now in a
liquid form flows through the heat exchanger 245 where the heat
transfer fluid is further sub-cooled prior to entering the
expansion device 250. The heat exchanger 245 may alternatively be
referred to as the suction-to-liquid line heat exchanger 245. The
heat exchanger 245 can further sub-cool the heat transfer fluid
which can, in an embodiment, increase a capacity of the first heat
transfer circuit 205. The heat transfer fluid, in a mixed liquid
and gaseous form, flows to the cascade heat exchanger 255.
At the cascade heat exchanger 255, the heat transfer medium in the
first heat transfer circuit 205 absorbs heat from the heat transfer
medium of the second heat transfer circuit 210, heating the heat
transfer fluid and converting it to a gaseous form. The gaseous
heat transfer fluid then flows through the second accumulator 260
and returns to the compressor 220. The above-described process can
continue while the heat transfer circuit 205 is operating (e.g.,
when the prime mover 215 is operating). In an embodiment, the
cascade heat exchanger 255 and the heat exchange relationship
between the first heat transfer circuit 205 and the second heat
transfer circuit 210 can increase an efficiency of the
refrigeration system by, for example, reducing an amount of energy
input via the power source 215 to maintain the one or more desired
conditions inside the transport unit 125 (FIG. 1). In an
embodiment, the reduction in energy input can, for example, reduce
an impact on the environment. In an embodiment, the cascade heat
exchanger 255 can reduce use of high pressure refrigeration
components (e.g., by enabling use of lower pressure heat transfer
fluids).
The second heat transfer circuit 210 can function according to
generally known principles in order to reject heat to the first
heat transfer circuit 205. The second compressor 275 compresses the
heat transfer fluid from a relatively lower pressure gas to a
relatively higher-pressure gas. The relatively higher-pressure gas
is discharged from the second compressor 275 and flows through the
cascade heat exchanger 255. In accordance with generally known
principles, the heat transfer fluid can be in a heat exchange
relationship with the heat transfer fluid of the first heat
transfer circuit 205 condenser 230 and can reject heat to the heat
transfer fluid of the first heat transfer circuit 205, thereby
cooling the heat transfer fluid of the second heat transfer circuit
210. The cooled heat transfer medium which is now in a liquid form
can flow through the third accumulator 280 to the second expansion
device 285. As a result, a portion of the heat transfer fluid is
converted to a gaseous form. The heat transfer fluid, which is now
in a mixed liquid and gaseous form, can flow to the evaporator 290.
At the evaporator 290, the heat transfer medium in the second heat
transfer circuit 210 can absorb heat from a heat transfer medium
(e.g., air), heating the heat transfer fluid and converting it to a
gaseous form. The evaporator fan 295, in accordance with generally
known principles, can aid in absorbing the heat from the heat
transfer fluid in the second heat transfer circuit 210. The
evaporator fan 295 can also, for example, blow air into the
conditioned space 150 in order to maintain the desired condition.
The gaseous heat transfer fluid can then return to the compressor
220. The above-described process can continue while the heat
transfer circuit 210 is operating.
FIG. 3A is a schematic diagram of a heat transfer circuit 300 which
can be included in place of the heat transfer circuit 210 (FIG. 2)
in the heat transfer system 200 (FIG. 2), according to an
embodiment. The heat transfer circuit 300 additionally includes a
flow control device 305. The flow control device 305 can be, for
example, a four-way valve, or the like. In operation, the flow
control device 305 can be used to modify the flow of the heat
transfer fluid in the heat transfer circuit 300. This can, for
example, enable the heat transfer circuit to be used in a cooling
mode (e.g., the second heat transfer circuit 210 as described in
accordance with FIG. 2 above) or in a heating mode, in which the
flow of the heat transfer fluid is reversed in order to reject heat
to the conditioned space 150 (FIG. 1) instead of rejecting heat
from the conditioned space 150.
FIG. 3B is a schematic diagram of a heat transfer circuit 310 which
can be included in place of the heat transfer circuit 210 (FIG. 2)
in the heat transfer system 200 (FIG. 2), according to an
embodiment. The heat transfer circuit 310 additionally includes a
hot-gas bypass flow 315 and a flow control device 320. The hot-gas
bypass flow 315 can be used, for example, to divert a portion of
heat transfer fluid to defrost the evaporator 290. The flow control
device 320 can be, for example, a solenoid valve (or similar type
of valve) which either enables or disables flow of the heat
transfer fluid. In an embodiment, the flow control device 320 can
have one or more intermediate positions in which flow of the heat
transfer fluid therethrough is partially enabled.
FIG. 4A is a schematic diagram of a heat transfer system 400A for a
TRS (e.g., the TRS 100 of FIG. 1), according to an embodiment. The
heat transfer system 400A includes a first heat transfer circuit
405A and a second heat transfer circuit 410A. In an embodiment, the
first heat transfer circuit 405A can alternatively be referred to
as the primary heat transfer circuit 405A, the high side heat
transfer circuit 405A, the condensing side heat transfer circuit
405A, the stage two heat transfer circuit 405A, or the like. In an
embodiment, the second heat transfer circuit 410A can alternatively
be referred to as the low side heat transfer circuit 410A, the
evaporating side heat transfer circuit 410A, or the like. The first
heat transfer circuit 405A is in thermal communication with the
second heat transfer circuit 410A. Aspects of the heat transfer
circuit 410A may be optional, as illustrated in dashed lines in the
figure.
Aspects of the heat transfer system 400A may be the same as or
similar to aspects of the heat transfer system 200 of FIG. 2.
The first heat transfer circuit 405A includes a compressor 415A, a
condenser 420A, an expansion device 425A, and a cascade heat
exchanger 430A. It will be appreciated that the first heat transfer
circuit 405A can include one or more additional components. For
example, the first heat transfer circuit 405A can include one or
more of the components shown and described in accordance with FIG.
4B below.
The compressor 415A, condenser 420A, expansion device 425A, and
cascade heat exchanger 430A are fluidly connected to form the first
heat transfer circuit 405A in which a heat transfer fluid can
circulate therethrough. The heat transfer fluid can generally be a
heat transfer fluid having a relatively low global warming
potential (GWP). Examples of suitable heat transfer fluids for the
first heat transfer circuit 405A can include, but are not limited
to, hydrofluoroolefins (HFOs), hydrocarbons (HCs), and carbon
dioxide (CO.sub.2) (also known by its ASHRAE Standard 34
designation R-744), or the like.
The second heat transfer circuit 410A includes a compressor 435A,
an expansion device 440A, and an evaporator 445A. The compressor
435A, cascade heat exchanger 430A, expansion device 440A, and
evaporator 445A are fluidly connected to form the second heat
transfer circuit 410A in which a heat transfer fluid can circulate
therethrough. The heat transfer fluid can generally be a heat
transfer fluid having a relatively low global warming potential
(GWP). Examples of suitable heat transfer fluids for the second
heat transfer circuit 410A can include, but are not limited to,
hydrofluoroolefins (HFOs), hydrocarbons (HCs), and carbon dioxide
(CO.sub.2) (also known by its ASHRAE Standard 34 designation
R-744), or the like. In an embodiment, the heat transfer fluid in
the first heat transfer circuit 405A and the heat transfer fluid
for the second heat transfer circuit 410A can be the same. In an
embodiment, the heat transfer fluid in the first heat transfer
circuit 405A and the heat transfer fluid for the second heat
transfer circuit 410A can be different.
The second heat transfer circuit 410A can include one or more
additional components. For example, in an embodiment, the second
heat transfer circuit 410A includes one or more of an intercooler
450A, a suction-liquid heat exchanger 455A, an expansion device
460A, and an economizer 465A. In an embodiment, the economizer 465A
can include an economizer heat exchanger. In an embodiment, the
economizer 465A can include a flash tank economizer.
In an embodiment, a location of the suction-liquid heat exchanger
455A and the economizer 465A can be switched. That is, in the
illustrated embodiment, the suction-liquid heat exchanger 455A is
disposed between the economizer 465A and the cascade heat exchanger
430A. In an embodiment, the economizer 465A can be disposed between
the suction-liquid heat exchanger 455A and the cascade heat
exchanger 430A. In an embodiment, the one or more additional
components can, for example, increase an efficiency of the heat
transfer system 400A. In an embodiment, the one or more additional
components can, for example, reduce a size of the cascade heat
exchanger 430A.
The compressors 415A and 435A can be driven by a power source
(e.g., the power source 215 in FIG. 2) (not shown in FIG. 4A).
In operation, the heat transfer system 400A can be used to maintain
a desired condition in the interior space 150 of the transport unit
125. More particularly, the first heat transfer circuit 405A may
receive heat that is rejected from the second heat transfer circuit
410A via the cascade heat exchanger 430A. The second heat transfer
circuit 410A can in turn be used to maintain the desired condition
within the interior space 150.
FIG. 4B is a schematic diagram of a heat transfer system 400B for a
TRS (e.g., the TRS 100 of FIG. 1), according to an embodiment. The
heat transfer system 400B includes a first heat transfer circuit
405B and a second heat transfer circuit 410B. In an embodiment, the
first heat transfer circuit 405B can alternatively be referred to
as the primary heat transfer circuit 405B, the high side heat
transfer circuit 405B, the condensing side heat transfer circuit
405B, the stage two heat transfer circuit 405B, or the like. In an
embodiment, the second heat transfer circuit 410B can alternatively
be referred to as the low side heat transfer circuit 410B, the
evaporating side heat transfer circuit 410B, or the like. The first
heat transfer circuit 405B is in thermal communication with the
second heat transfer circuit 410B. Aspects of the heat transfer
circuit 405B may be optional, as illustrated in dashed lines in the
figure.
Aspects of the heat transfer system 400B may be the same as or
similar to aspects of the heat transfer system 200 of FIG. 2.
The first heat transfer circuit 405B includes a compressor 415B, a
condenser 420B, an expansion device 425B, and a cascade heat
exchanger 430B.
The compressor 415B, condenser 420B, expansion device 425B, and
cascade heat exchanger 430B are fluidly connected to form the first
heat transfer circuit 405B in which a heat transfer fluid can
circulate therethrough. The heat transfer fluid can generally be a
heat transfer fluid having a relatively low global warming
potential (GWP). Examples of suitable heat transfer fluids for the
first heat transfer circuit 405B can include, but are not limited
to, hydrofluoroolefins (HFOs), hydrocarbons (HCs), and carbon
dioxide (CO.sub.2) (also known by its ASHRAE Standard 34
designation R-744), or the like.
The first heat transfer circuit 405B can include one or more
additional components. For example, in an embodiment, the first
heat transfer circuit 405B includes one or more of a suction-liquid
heat exchanger 470B, an economizer 475B, and an expansion device
480B. In an embodiment, the economizer 475B can include an
economizer heat exchanger. In an embodiment, the economizer 475B
can include a flash tank economizer. In an embodiment, the one or
more additional components can, for example, increase an efficiency
of the first heat transfer circuit 405B, and accordingly, the heat
transfer system 400B.
The second heat transfer circuit 410B includes a compressor 435B,
an expansion device 440B, and an evaporator 445B. It will be
appreciated that the second heat transfer circuit 410B can include
one or more additional components. For example, the second heat
transfer circuit 410B can include one or more of the components
shown and described in accordance with FIG. 4A above.
The compressor 435B, cascade heat exchanger 430B, expansion device
440B, and evaporator 445B are fluidly connected to form the second
heat transfer circuit 410B in which a heat transfer fluid can
circulate therethrough. The heat transfer fluid can generally be a
heat transfer fluid having a relatively low global warming
potential (GWP). Examples of suitable heat transfer fluids for the
second heat transfer circuit 410B can include, but are not limited
to, hydrofluoroolefins (HFOs), hydrocarbons (HCs), and carbon
dioxide (CO.sub.2) (also known by its ASHRAE Standard 34
designation R-744), or the like. In an embodiment, the heat
transfer fluid in the first heat transfer circuit 405B and the heat
transfer fluid for the second heat transfer circuit 410B can be the
same. In an embodiment, the heat transfer fluid in the first heat
transfer circuit 405B and the heat transfer fluid for the second
heat transfer circuit 410B can be different.
The compressors 415B, 435B can be driven by a power source (e.g.,
the power source 215 in FIG. 2) (not shown in FIG. 4B).
In operation, the heat transfer system 400B can be used to maintain
a desired condition in the interior space 150 of the transport unit
125. More particularly, the first heat transfer circuit 405B may
receive heat that is rejected from the second heat transfer circuit
410B via the cascade heat exchanger 430B. The second heat transfer
circuit 410B can in turn be used to maintain the desired condition
within the interior space 150.
It is to be appreciated that aspects of FIGS. 4A and 4B can be
combined. For example, a heat transfer system can include the first
heat transfer circuit 405A and the second heat transfer circuit
410B. In an embodiment, a heat transfer system can include the
first heat transfer circuit 405B and the second heat transfer
circuit 410A.
Aspects:
It is noted that any one of aspects 1-12 below can be combined with
any one of aspects 13-23, 24-26, and/or 27-28. Any one of aspects
13-23 can be combined with any one of aspects 24-26 and/or 27-28.
Any one of aspects 24-26 can be combined with any one of aspects
27-28.
Aspect 1. A transport refrigeration system (TRS), comprising:
a first heat transfer circuit, including: a first compressor, a
condenser, a first expansion device, and a cascade heat exchanger,
wherein the first compressor, the condenser, the first expansion
device, and the cascade heat exchanger are in fluid communication
such that a first heat transfer fluid can flow therethrough;
and
a second heat transfer circuit, including: a second compressor, the
cascade heat exchanger, a second expansion device, and an
evaporator, wherein the second compressor, the cascade heat
exchanger, the second expansion device, and the evaporator are in
fluid communication such that a second heat transfer fluid can flow
therethrough;
wherein the first heat transfer circuit and the second heat
transfer circuit are arranged in thermal communication at the
cascade heat exchanger such that the first heat transfer fluid and
the second heat transfer fluid are in a heat exchange relationship
at the cascade heat exchanger.
Aspect 2. The TRS according to aspect 1, further comprising a prime
mover configured to provide mechanical power to the first
compressor.
Aspect 3. The TRS according to aspect 2, further comprising a
generator connected to the prime mover such that the prime mover
provides mechanical power to the generator, wherein the generator
is electrically connected to the second compressor to provide an
electric power to the second compressor.
Aspect 4. The TRS according to any one of aspects 1-3, wherein the
first heat transfer fluid and the second heat transfer fluid are
different.
Aspect 5. The TRS according to any one of aspects 1-4, wherein the
first heat transfer fluid has a relatively low global warming
potential (GWP).
Aspect 6. The TRS according to aspect 5, wherein the first heat
transfer fluid is an unsaturated hydrofluorocarbon (HFC).
Aspect 7. The TRS according to aspect 6, wherein the first heat
transfer fluid is one of a hydrofluoroolefin (HFO), a hydrocarbon
(HC), ammonia, or carbon dioxide (CO.sub.2).
Aspect 8. The TRS according to any one of aspects 1-7, wherein the
second heat transfer fluid is carbon dioxide (CO.sub.2).
Aspect 9. The TRS according to any one of aspects 1-8, wherein the
second heat transfer circuit further includes a four-way flow
control device.
Aspect 10. The TRS according to any one of aspects 1-9, wherein the
second heat transfer circuit further includes a hot-gas bypass.
Aspect 11. The TRS according to any one of aspects 1-10, wherein
the second heat transfer circuit further includes one or more of an
intercooler, a suction-liquid heat exchanger, and an
economizer.
Aspect 12. The TRS according to any one of aspects 1-11, wherein
the first heat transfer circuit further includes one or more of a
suction-liquid heat exchanger and an economizer.
Aspect 13. A system, comprising:
an internal combustion engine;
a first heat transfer circuit, including: a first compressor, a
condenser, a first expansion device, and a cascade heat exchanger,
wherein the first compressor, the condenser, the first expansion
device, and the cascade heat exchanger are in fluid communication
such that a first heat transfer fluid can flow therethrough;
and
a second heat transfer circuit, including: a second compressor, the
cascade heat exchanger, a second expansion device, and an
evaporator, wherein the second compressor, the cascade heat
exchanger, the second expansion device, and the evaporator are in
fluid communication such that a second heat transfer fluid can flow
therethrough;
wherein the first heat transfer circuit and the second heat
transfer circuit are arranged in thermal communication at the
cascade heat exchanger such that the first heat transfer fluid and
the second heat transfer fluid are in a heat exchange relationship
at the cascade heat exchanger.
Aspect 14. The system according to aspect 13, further comprising a
generator coupled to the internal combustion engine, wherein the
generator is configured to provide an electrical power to the
second compressor.
Aspect 15. The system according to any one of aspects 13-14,
wherein the first heat transfer fluid and the second heat transfer
fluid are different.
Aspect 16. The system according to any one of aspects 13-15,
wherein the first heat transfer fluid has a relatively low global
warming potential (GWP).
Aspect 17. The system according to aspect 16, wherein the first
heat transfer fluid is an unsaturated hydrofluorocarbon (HFC).
Aspect 18. The system according to aspect 17, wherein the first
heat transfer fluid is one of a hydrofluoroolefin (HFO), a
hydrocarbon (HC), ammonia, or carbon dioxide (CO.sub.2).
Aspect 19. The system according to any one of aspects 13-18,
wherein the second heat transfer fluid is carbon dioxide
(CO.sub.2).
Aspect 20. The system according to any one of aspects 13-19,
wherein the second heat transfer circuit further includes a
four-way flow control device.
Aspect 21. The system according to any one of aspects 13-20,
wherein the second heat transfer circuit further includes a hot-gas
bypass.
Aspect 22. The system according to any one of aspects 13-21,
wherein the second heat transfer circuit further includes one or
more of an intercooler, a suction-liquid heat exchanger, and an
economizer.
Aspect 23. The system according to any one of aspects 13-22,
wherein the first heat transfer circuit further includes one or
more of a suction-liquid heat exchanger and an economizer.
Aspect 24. A method of heat transfer in a transport refrigeration
system (TRS), the TRS having a first heat transfer circuit and a
second heat transfer circuit in thermal communication via a cascade
heat exchanger, the method comprising:
circulating a first heat transfer fluid through the first heat
transfer circuit;
circulating a second heat transfer fluid through the second heat
transfer circuit; and
exchanging heat between the first heat transfer fluid and the
second heat transfer fluid via the cascade heat exchanger.
Aspect 25. The method according to aspect 24, wherein exchanging
heat between the first heat transfer fluid and the second heat
transfer fluid via the cascade heat exchanger includes rejecting
heat from the second heat transfer fluid to the first heat transfer
fluid.
Aspect 26. The method according to aspect 25, wherein the second
heat transfer circuit is in thermal communication with a
conditioned space of the TRS, and the method further includes
controlling one or more environmental conditions in the conditioned
space with the second heat transfer circuit.
Aspect 27. A transport refrigeration system (TRS), comprising:
a first heat transfer circuit, including: a first compressor, a
condenser, a first expansion device, an economizer, a second
expansion device, and a cascade heat exchanger, wherein the first
compressor, the condenser, the first expansion device, the
economizer, the second expansion device, and the cascade heat
exchanger are in fluid communication such that a first heat
transfer fluid can flow therethrough; and
a second heat transfer circuit, including: a second compressor, an
intercooler, the cascade heat exchanger, a suction-liquid heat
exchanger, a third expansion device, and an evaporator, wherein the
second compressor, the intercooler, the cascade heat exchanger, the
suction-liquid heat exchanger, the third expansion device, and the
evaporator are in fluid communication such that a second heat
transfer fluid can flow therethrough;
wherein the first heat transfer circuit and the second heat
transfer circuit are arranged in thermal communication at the
cascade heat exchanger such that the first heat transfer fluid and
the second heat transfer fluid are in a heat exchange relationship
at the cascade heat exchanger.
Aspect 28. The TRS according to aspect 27, wherein the economizer
is one of an economizer heat exchanger and a flash tank
economizer.
The terminology used in this specification is intended to describe
particular embodiments and is not intended to be limiting. The
terms "a," "an," and "the" include the plural forms as well, unless
clearly indicated otherwise. The terms "comprises" and/or
"comprising," when used in this specification, specify the presence
of the stated features, integers, steps, operations, elements,
and/or components, but do not preclude the presence or addition of
one or more other features, integers, steps, operations, elements,
and/or components.
With regard to the preceding description, it is to be understood
that changes may be made in detail, especially in matters of the
construction materials employed and the shape, size, and
arrangement of parts without departing from the scope of the
present disclosure. This specification and the embodiments
described are exemplary only, with the true scope and spirit of the
disclosure being indicated by the claims that follow.
* * * * *